In many manufacturing plants or other facilities, such as papermills, where large pumps are run continuously to convey a process liquid for a mixing process, cooling and lubricating mediums such as water or oil are often used to cool and lubricate the mechanical seals or packings surrounding the drive shafts of the pumps. The heat generated due to friction of the drive shaft with the sides of the impeller housing and the high temperature to which the process liquid is generally heated can cause the failure of the seals, which can result in expensive pump down time.
When the seal fails, the process liquid can leak out of the apparatus or the cooling water will leak in, mixing with the process liquid. Such leaks waste water and waste energy as the mixing of cooling water with the process liquid lowers the temperature of the process liquid, requiring additional energy and thus additional expense to be expended to maintain the temperature of the process liquid at the proper processing level. It is therefore highly desireable to detect a breach of the seal of a pump as early as possible so that the seal can be repaired or replaced, thereby restoring the efficiency of the process and prolonging the life of the pump.
In general, flowmeters are used to monitor and regulate the flow of sealing water about a pump seal. Flowmeters measure the pressure and rate of flow of the sealing water thereby to provide an indication of the integrity of the pump seal. If the flow increases and pressure drops, it is an indication that the sealing water is leaking into the process liquid. If the flow drops and pressure rises, it is an indication of a leak of the process liquid out of the process. Thus, flowmeters provide an indication of the incipient failure of the pump seal.
However, the water used to cool and lubricate pump seals in most processing plants is generally waste or river water which has a considerable amount of dirt and other impurities in it. As a consequence, this dirt and grime tends to accumulate within the flow tube of the flowmeter. This accumulation of dirt clouds the flow tube and restricts the flow through the flow tube, making it difficult to read and take accurate measurements of the rate of the flow.
Flowmeters having a cleaning function for cleaning the flow tube of the flowmeter have been developed. Such flowmeters generally include a movable float mounted on a conically shaped rod extending completely along the length of the flow tube. However, the cleaning function of these conventional flowmeters only takes place in a section of the flow tube between the zero indicator and the float which gives the current flow indication as the expanding diameter of the conical rod limits the travel of the float along the length of the flow tube. Consequently, there is a portion of the flow tube from which accumulated dirt and grime are not cleaned. Thus, the cleaning function performed by conventional flowmeters is incomplete and thereby fails to correct the inaccuracy of the flowmeter.
Therefore, it can be seen that a need has existed for a flowmeter which has a self-cleaning function that quickly and completely cleans the flow tube thereof of any accumulated dirt and debris. Accordingly, it is the provision of a flowmeter with an improved self cleaning function to which the present invention is primarily directed.